Electroacoustical apparatus



@st 331, 11939 L. J. ANDERsbN ELECTROACOUSTICAL APPARATUS Filed March 51, 1956 M w W0 N T R NA m W M m:

[Y AB Patent ed Oct. 31,1939 I A UNITED STATES PATENT, OFFICE ELEOTROACQUSTICAL APPARATUS Leslie J. Anderson, Westmont, N.-J., assignor to. a Radio Corporation of America, a corporation of Delaware 1 Application March 31, 1936, Serial No. 71,849

- I s Claims. (01. 115-21) This invention relates toelectroacousticai appaeach other or with the magnet, whereby the pole ratus, such as microphones, pick-up devices, and pieces are drawn into firm en ag ment with the the like, and more particularly to the means in magnet. -such apparatus for maintaining the magnet struc- The novel features that I consider characterture and pole piece structure in clamped relation. istic of my invention are set forth with particu- 5 It'has been customary, in devices of this sort, larity in the appended claims. The invention to tap the-ends'of the magnets and secure the POL itself, however, as well as the method of operapieces thereto by means of screws, for example. tion thereof, together with additional objects and I Considerable diflicult has, however, been experiadvantages thereof, will best be understood from enced in holdingthe magnets in place, particuthe followingdes'cription of a specific embodil0 larly in various typesof velocity microphones, for m'ent thereof, when read in connection with the the reason that the magnets are formed of very accompanying drawing in which, hard steel which is difficult to drill and tap: The Fig. 1 is a front elevation, partially in section, problem is additionally difficult because the clamp showing my improved clamping means applied must be so designed that it will not disturb the to a U-shaped magnet and its associated pole 15 acoustic performance of the microphone. pieces, and I The'primary object of my invention is to pro- Fig. 2 is a side elevation thereof. vide improved clamping means for clamping to- Referring more specifically to the drawing,

gether the magnet and pole piece structures, wherein similar reference characters designate which clamping means will be free from the discorresponding parts throughout, there is shown 20 advantages ofprior artclamping devices. a U-shaped magnet l on the ends of which rest More specifically, it is an object of my invention the pole pieces 3 and 5 having lateral extensions to provide "improved clamping means, as aforel and 9, respectively. Embracing the magnet i saidpwhich will not only maintain the magnet around its periphery is a thin, resilient strip H, and pole piece structures in properly cooperable preferably of brass, the ends of which are bent g5 relation, but which will not disturb the acoustic around the extensions'l and 9 in spaced relaperformance of microphones in which the clamption thereto, as clearly shown in Fig. 1. The ends ing structure is embodied. of the resilient strip 1 I may be reinforced by sheet A further'object of my invention is to provide brass plates l3, as by brazing or the like. 0 an improved clamping device of the type described Threadedly received within the ends of the which will beadjustable to clamp the pole pieces strip H and the plates l3 are the screws l5 and to the magnet with a variable clamping force. I! which bear, respectively, against the lateral Still a further object of my invention is to proextensions I and 9, while a plurality of screws vide improved clamping structure, as aforesaid, l9 and 2| are loosely received in the ends of the by means of which the danger of disturbing the strip H and the plates 13 and are threaded into 5 relation between the pole pieces and the magnet the extensions 1 and 9, respectively, of the pole by reason of mechanical shock will be practically pieces 3 and 5. The pole pieces 3 and 5 are conentirely eliminated. nected to each other in any suitable way, as by Another object of my invention is to provide a pair of screws 23 which are threaded therein and 0 improved clamping structure of the type set forth are received by a block 25 of insulating material which will permit conservation of space and between which and a conducting strip 21 is structure. clamped one end of a conductive ribbon 29 It is another object of my invention to provide mounted for vibratlle movement in the air gap improved-clamping means of the type aforesaid between the pole pieces'3 and 5. In operation, which is very simple in construction, which is as the screws ll are advanced in the plates I3, economical of manufacture, which maybequickly they draw the resilient strip ll tightly against and easily applied in place during assembly, and the magnet I, while at the same time applying which is highly efliclent in operation. a force against the pole piece extensions 1 and 9 In accordance with my invention, I provide a in the direction of the arms of the magnet. The thin, resilient strip which is arranged to embrace screws l9 and 2| may also be adjusted to prevent the magnet and is adiustably secured to the pole tilting of the plates IS with respect to the pole pieces resting on the ends of the magnet in a piece extensions I and 9 under the influence of manner such that the resilient strip may be drawn the screws l5 and II. It will therefore be seen tightly against the magnet without materially that, by means of the difierential action between u affecting the alignment of the pole pieces with the two sets of screws llil9, and |l-2i, it is possible. to draw the clamp H up tightly and evenly without ailfecting the alignment of the pole pieces and the magnet.

Although I have shown and described but a single embodiment of my invention, I am fully aware that many modifications thereof are possible. For example, in place of the screws li-IS and l'|2l, any suitable means may be provided which will place the clamp I I under tension upon relative adjustment of said means. Also, in place of a single magnet, a plurality of magnets may be used as, for example, a pair of magnets each associated with corresponding ends of extensions 1 and 9. Many other changes will, no doubt, readily suggest themselves to those skilled 'in the art. I desire, therefore, that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit and scope of the appended claims.

I claim as my invention; v

1. In electromagnetic apparatus, a magnet; a plurality of \pole pieces associated with said magnet, resilient means embracing said magnet and at least a portion of said pole pieces for main-- taining said pole pieces in cooperative relationwith said magnet, and relatively adjustable means associated with said resilient 'means and with each of said pole pieces for placing said resilient means under tension whereby to cause said resilient means to draw said pole pieces firmly against said magnet, said relatively adjustable means being adjustably received by said resilient means and arranged to apply a force on its associated pole piece in a direction toward said magnet.

2. In electromagnetic apparatus, a magnet, a

said resilient means and is arranged to apply a.

force on its associated pole piece in a direction toward said magnet, and the other of which is adjustably received in its associated pole piece and is arranged to limit the relative movement between said resilient means and said pole piece.

*3. In electromagnetic apparatus, a U-shaped magnet, a pole piece associated with each endoi' said magnet, means connecting said pole pieces to .each other against relative displacement, .a

resilient strip in engagement with the periphery of said magnet and having its ends bent around aportion of said pole pieces, a screwextending loosely through each end of said strip and threadedly receivedin its associated pole piece, and a second screw threadedly received in each end of said resilient strip and bearing against its associated pole piece, the-difierentialaction between said screws serving to tension said strip whereby to draw said pole pieces into firm engagement with said magnet while maintaining said pole pieces and magnet in aligned relation.

LESLIE J. ANDERSON. 

